Answer:
1. Essential Amino Acids: are those amino acids that can’t be synthesized by the body and must be taken from some outside source. For example Histidine. It has a carboxylic acid group and an imidazole side chain. It can be found in protein histamine where it is a radical histidyl precursor.
2. Non-essential Amino Acids: are those that our body can easy synthesize mostly by Glucose metabolism. For example, Glutamic acid that is found in most protein structures of excitatory neurotransmitters.
3. Conditional Amino Acids: are non-essential except at times of need for example ornithine. It can be found in the processing of Urea cycle.